A variety of lactic streptococcus which is unusual in its growth requirements is described. The culture grows on an agar medium (based on B.D.H. peptone) only under conditions of semi-anaerobiosis. It will grow on the surface, however, if the medium is altered in certain respects, for example: (a) if the B.D.H. peptone is replaced by tryptone, the only peptone which appears to stimulate rapid aerobic growth of the organism; or (b) the lactose in the medium is replaced by glucose; or (c) the pH of the medium is reduced.

Different metabolic mechanisms appear to be involved according to the composition of the medium.

The culture is more sensitive to changes in milk composition than are other strains of lactic streptococci.

The general experience of the retail milk trade is that considerable variations exist in the demand for milk and cream at different times of the year, and that these need careful consideration to preserve the proper balance between the supply of, and demand for milk. Different social classes of consumers are also known to exhibit different habits of milk and cream consumption. This paper examines the fluctuations of demand for milk and cream over a 1-year period of four social classes of consumers.

There can now be little doubt that glucose is the principal precursor of lactose in the mammary gland. Evidence for this comes form in vivo and in vitro studies, using both analytical and isotopic techniques (1), though considerable species differences have been noted.

When milk was chilled for 12 and 24 h at 0 °C, a decrease in the calcium and phosphorus contents of the casein micelle of both buffalo and cow's milk was observed. This decrease was directly proportional to the cooling period. A proportionate increase with cooling in the sialic-acid content of the casein micelle of chilled milk was noticed. Casein micelle isolated from chilled milk exhibited low opacity compared with the normal counterpart.

A decrease in micellar casein and an increase in soluble casein were observed in both buffalo and cow's milk, in proportion to the cooling period. Similar results were obtained when casein micelles were resuspended in milk dialysate and centrifuged.

Casein micelles from chilled milk showed different patterns on starch-gel electrophoresis compared with normal micelles. The intensity of the κ-casein band was relatively higher in the chilled samples. Gel-filtration studies suggest that some molecular rearrangement occurs in the casein micelle when milk is chilled.

The release of sialopeptide from micellar casein by rennet was not influenced by chilling. However, a decrease in the rate of turbidity development in renneted suspensions of casein micelles was noted in chilled milk, which suggests a change in the structure of the casein micelle.

No difference was noticed between buffalo and cow's milk in these respects.

1. The colours of the butter for individual cows at the London Dairy Show have been measured on a colour scale of yellow shades on cellulose strips, and the results analysed statistically.

2. The mean values and variability curves of the ranges of butter colour in the different breeds of dairy cattle are given. Circumstances which may affect these values are indicated.

3. The two most important factors affecting butter colour are the genetic character of the cow and the method of feeding.

4. A slight increase in the shade of colour was found to occur under most of the various conditions which give rise to increased milk yield. It is suggested that this may be due to the greater intake of colouring matter (associated with the greater food intake) in proportion to butterfat produced, since increase in yield is usually associated with decrease in fat percentage.

Unwrapped samples of salted sweet-cream butter were stored in darkness at 1°C for 6–8 weeks over silica gel, water, isotonic salt solutions, and in free air. Moisture and fat peroxide gradients from the surfaces to the interior of the stored samples were measured in thin sections obtained by a simple macrotome technique. The surface oxidized at the same rate as the rest of the butter and its rate of oxidation was not affected by moderate drying or moisture uptake. With severe surface drying, especially when induced by silica gel, fat oxidation was inhibited, while moisture uptake by the more heavily salted butters promoted surface oxidation.

All teats of a herd of lactating cows were contaminated after each milking with Staphylococcus aureus. Two teats of each cow were subsequently dipped in an iodine solution, while the remaining 2 teats were not dipped. For cows with a single infection the interval to infection in dipped and undipped quarters was 64 and 60 d respectively, while for the first infected quarter of cows with multiple infections the interval to infection in dipped and undipped quarters was 50 and 39 d respectively. For the second quarter infected in cows with multiple infections, the period between the first and second infection was 21 and 12 d for dipped and undipped quarters respectively. It is suggested that while teat skin disinfection was effective in reducing the rate of new infection, it had little effect on the process of infection in those quarters becoming infected. The occurrence of an infection in one quarter doubled the rate of infection in the other quarters.

If research work in cheese ripening is to be conducted on an entirely satisfactory basis, a complete control of both temperature and humidity of the ripening room must be available.

Though temperatures are relatively easily controlled, the factor of shrinkage or loss of moisture from the cheese is a more difficult problem. Further, should such loss of moisture be an additional and variable factor due to differences in humidity of the ripening room, research work in cheese ripening is seriously handicapped. It is realised that different cheese, whether large or small, high or low in moisture, new or mature, lose moisture at different rates even though kept under exactly the same conditions of storage. Also, the identical cheese cease to remain the same due to various rates of ripening, if studied as to their loss of moisture at different temperatures.

The reactions which occur when sour cream is “neutralised” with calcium hydroxide and sodium bicarbonate are discussed from the point of view of the acid-base equilibria.

Experimental results are recorded showing that:

1. When lime is the neutraliser, pasteurisation has little effect on the pH. or titratable acidity of the neutralised cream.

2. The reduction in acidity when lime is used is shown to vary from that calculated from the sodium hydroxide titration to an extent which depends on the pH of the neutralised cream. The reasons for and extent of this variation are defined.

3. When sodium bicarbonate is used as a neutraliser the loss of carbon dioxide (which is influenced by the method of pasteurisation adopted) has most influence on the degree of neutralisation obtained and the experiments show the extent of this at various acidities.

The variations in the pH-titratable acidity relationship of creams neutralised with calcium hydroxide and sodium bicarbonate are defined.

Following the earlier papers in this series ((1)–(4)) further work has been carried out on the fats and greases which attack milking rubbers. The sources from which they come have been investigated and an estimate made of the composition of the fatty material obtained from used milk liners.

The nutritional deficiencies of co-precipitate as a growth medium for a strain of Lactobacillus acidophilus have been studied. Acid production by this organism was insignificant in a medium composed of 4% low-calcium co-precipitate and 5% lactose.

Additions of the amino acids phenylalanine, tyrosine, valine, cysteine and threonine as well as of nicotinic acid, manganese, magnesium and citric acid all increased acid production.

When only half the milk solids of skim-milk powder was replaced by the coprecipitate, fortification with manganese only was required.

1. Colon bacilli grown in milk for from 3 to 16 hours partially inhibit the subsequent formation of acid by lactic streptococci.

2. The inhibition is not entirely accounted for by the increased hydrogenion concentration nor by the lactic acid produced by the colon bacilli. Other substances which have a retarding influence on the streptococci are evidently formed in milk cultures of colon bacilli. The action of these substances is not significantly modified by heating at 75°C. for one hour.

3. The possible practical significance of the phenomenon is discussed.

Kizer, Hankin, Speck & Aurand(1) have observed that the impurities associated with proteolytic enzymes are stimulating to lactic acid bacteria, and they have suggested that these substances may accelerate the ripening of dairy products. In view of these observations and suggestions an experiment begun in March 1954, on the preparation of cheese with crystalline rennin, is reported below. The results are in agreement with the suggestions of Kizer et al.

The changes in the size of the milking and residual fractions following milking intervals of 4, 8, 12, 16, 20 and 24 h were investigated in 18 ewes receiving regular injections of oxytocin at each milking. The observations were carried out using a 6×6 Latin square design in which each treatment interval was repeated 4 times. The milking and the residual fractions were found to increase significantly with the lengthening of the interval. The amount of hand strippings was also related to interval length. When a given interval was repeated there were no changes in the relative sizes of the fractions. A change in the milking interval, however, caused significant changes in the various fractions. It is suggested that in the present experiment the milking fractions consisted in the main of milk that was present in the sinuses prior to milking.

In five untreated goats, mammary extraction of plasma triglycerides increased at parturition. In five goats that had as much secretion as possible regularly removed from one mammary gland beginning on d 143 of gestation, the change of triglyceride extraction occurred several d before parturition in the emptied gland but at parturition in the contralateral control gland. The experimentally induced early increase of extraction of plasma triglycerides preceded the increase of prostaglandin Fα concentration in mammary secretion at parturition, and occurred despite abnormally high concentrations of progesterone in the secretion.

In a preliminary investigation into the experimental error of the plate count examination of butter, 154 boxes of choicest quality butter were examined by plating in triplicate, in a dilution of 1/500, each of three 1 g. samples per box.

X2 tests in both this and a later series indicated that the means of the triplicate counts in respect of plates averaging less than 300 colonies gave, in the main, reasonably satisfactory estimates of the bacterial content of the samples. In two of the tests, however, excessive within-sample variability was shown by abnormally high values obtained from the summation of x2. This is accepted as an indication that the plate count was not always a reliable index of the sample population.

The between-sample variability in this series has been shown by transforming the counts to logarithms and calculating the coefficient of variation in respect of each box. In the distribution of the coefficients approximately 50% were found to lie on either side of a 4·0% level, while 10% gave values higher than 14·0%.

In a further inquiry twelve boxes of butter were selected for quality and uniformity and data were secured from the examination of seven 1 oz. samples selected at random from each box.

Treatment of the results by the method of analysis of variance, using a square root transformation, indicated that the estimates of within-sample variance obtained could be regarded as estimates of a common variance. Highly significant differences were found, however, among the between-sample mean squares, and the variability was found to be excessive in six of the twelve boxes examined.

No significant general correlation was found in this series between bacterial counts and either salt or moisture determinations.

The application of these results to research problems and to routine tests involving the estimation of bacterial numbers in butter is discussed.

An apparatus has been developed for the routine estimation of oxygen in the headspace gas of tins of dried milk. The sampling device is an integral part of the apparatus, which is constructed mainly of metal and is simple to operate. As many as twenty samples may be taken and analysed in an hour.

Our thanks are due to the Drawing Office and Workshop staffs of the Division of Industrial Chemistry, Council for Scientific and Industrial Research, who designed and manufactured the equipment, and to the Maffra Co-operative Milk Products Co. Ltd., who permitted the apparatus to be tested in their laboratories under factory conditions.

The aim of the research described here was to investigate the in vitro immunomodulatory effects of 3RS, 7R, 11R-phytanic acid (3RS-PHY) from the perspective of efficacy against autoimmune diseases. 3RS-PHY is a milk component with strong agonist activity at the peroxisome proliferator activated receptor (PPAR). As PPAR is a therapeutic target for several human diseases, 3RS-PHY intake may have possible health benefits. Recently, we chemically synthesized a preparation of 3RS-PHY and demonstrated that 3RS-PHY inhibited T-cell production of interferon (IFN)-γ. However, the overall immunomodulatory effects were not evaluated. In this study, mouse splenocytes, purified T-cells and B-cells were stimulated by mitogens and incubated with 3RS-PHY, followed by evaluation of cytokine and antibody production. A macrophage-like cell line J774.1 was also incubated with 3RS-PHY to evaluate nitric oxide production. 3RS-PHY decreased mRNA levels not only of IFN-γ but also of interleukin (IL)-2, IL-10 and IL-17A in splenocytes and similar effects were confirmed at the protein level. In addition, 3RS-PHY had a direct action on T-cells with preferential inhibitory effects on Th1 and Th17 cytokines such as IFN-γ and IL-17A. Furthermore, 3RS-PHY suppressed antibody secretion by B-cells and nitric oxide production by J774.1 almost completely, indicating that 3RS-PHY is a bioactive fatty acid with anti-inflammatory properties. These findings encourage further investigations, including in vivo experiments, to evaluate whether 3RS-PHY actually shows the potential to prevent autoimmune diseases, and provide basic information to produce milk and dairy products with an increased 3RS-PHY concentration.

This study was conducted to determine the effect of acidophilus yoghurt (yoghurt fortified with Lactobacillus acidophilus) in comparison to traditional plain yoghurt (St. thermophilus and L. bulgaricus starter cultures) on the survival of three pathogenic Escherichia coli strains; Shiga toxigenic O157 (STx O157), non-toxigenic O157 (Non-STx O157) and Shiga toxigenic non-O157 (STx O145). After six days of refrigerated storage of laboratory-manufactured yoghurt inoculated with the three strains of E. coli separately, all were eliminated in acidophilus yoghurt, while their survival extended in the traditional yoghurt along the storage period (17 d). Reduction percentages of the tested strains in acidophilus yoghurt were 99.93, 99.93 and 99.86%, with log reduction of 3.176, 3.176, and 2.865 cfu/g for Stx O157, Non-Stx O157, and Stx O145 E. coli, respectively, in comparison to 91.67, 93.33 and 93.33%, with log reduction of 1.079, 1.176 and 1.176 cfu/g in traditional yoghurt. Statistical analysis showed a significant effect of acidophilus yoghurt in reducing the count of Stx E. coli O157 (P = 0.001), Non-Stx E. coli O157 (P < 0.01) and Stx E. coli O145 (P < 0.01) compared to the traditional yoghurt. These findings emphasize the potential use of acidophilus yoghurt as a biocontrol alternative method for eliminating pathogenic E. coli, as well as other similar applications in the dairy industry.

Hydrogenated milk fats have been subjected to a process of fractional melting. In five of the six samples, the procedure yielded two fractions, defined as oil/upper solid and lower solid fractions, whilst in the remaining sample, three fractions (oil, upper solid and lower solid) were obtained. The oil and oil/upper solid fractions were rich in short-chain fatty acids (FA) (4:0 and 6:0), whereas the lower solid fractions contained large amounts of long-chain FA (16:0 and 18:0). Triglyceride distributions reflected these differences in FA composition, the oil and oil/upper solid fractions being dominated by triglycerides with carbon numbers (CN) 36–38; the dominant CN for the lower solid fraction was 48–54. Melting spectra, obtained using differential scanning calorimetry, showed that the ability of the fractionation procedure to separate on the basis of melting properties ranged from excellent to relatively poor, depending on the type of milk fat.